Valve tube and casing therefor



May 5, 1942. .1, J. Hr-:GER

VALVE TUBE AND, cAsING T HEnEFoa File'd Aug. 2, 1940 nia lll/l1'Illl/llllllIl/ll,

Patented May 5, 1942 IUNITED STATES PATENT OFFICE VALVE TUBE-'AND CASINGTHEREFOR Joseph J. Heger, Chicago, Ill., assigner vto Universal X-RayProducts, Inc., Chicago, Ill.,

corporation of Illinois Application August 2, 1940, Serial No. 349,509

' 6 claims.

Myiinvention relates to a thermionic valve arrangement, and inparticular to a rectiiier tube suitable for use with an X-ray producingdevice.

It is an object, of my invention to provide an improved thermionic valvearrangement of this type in which the valve is eiectively cooled. Myinvention preferably contemplates a thermionic valve comprising acathode having an electron emitting filament and anV anode for receivingelectrons from the cathode, both sealed Vin an envelope of electricalinsulating material, and it is an objectl of my invention to provide animproved arrangement of this type in which a liquid circulates aboutandin contact with the anode adjacent the electron receiving faceportions thereof for cooling it.`

It is another object of my invention to provide an improved thermionicvalve arrangement of this type in which the valve is short and compactbut has nevertheless a suiiiciently large electrical resistance betweenits cathode and anode to withstand the high voltages used with Y-raytubes.

It is a further object of my invention to provide an improved thermionicvalve arrangement of this type in which the electron emitting lilamentof the valve is eiectively supported in order that the valve may bemounted in any position without danger of breakage of the iilament. Y

It is still another` object of my invention to provide an improvedarrangement of this type in which the electron emitting lament of thevalve is eiectively shielded electrostatically from the anode.

It is still a further object of my invention to provide an improvedarrangement of this type in which the thermionic valve is of simpleconstruction and may be economically manufactured.

My improved thermionic valve arrangement preferably comprises a tube ofelectrical insulating material formed with a reentrant portion eX-tending from one of its ends along the tube Walls, a cup-like anode forcompleting the tube sealed substantially at its open end to saidreentrant portion and having its sides separated from said reentrantportion, a cooling liquid circulatingv about the anode, a cathode havingan electron emitting filament positioned in the anode and surrounded bya plurality of spaced metal posts for electrostatically shielding theiilament, and a plurality of supporting members fastened to certain ofthe metal posts and supporting the lament at intermediate pointsthereof.

(Cl. Z50-27.5)

The invention consists in the novel constructions, arrangements anddevices to be hereinafter described and claimed for carrying out vtheabove stated objects and such other objects as will appear from thefollowing description of a certain preferred embodiment illustrated inthe accompanying drawing, wherein- Fig. 1 is a longitudinal sectionalview of a rec,- tiiier tube involving the principles of my invention;

Figs. 2, 3, 4 and 5 aresectional views of the tube taken on lines 2-2,3-3, 4 4 and 5 5 respectively of Fig. 1; and

Fig. 6 is a sectional view on a smaller scale of X-ray apparatusincluding my improved tube.

Like characters of reference designate like parts in the several views.i

Referring now to the drawing, the illustrated embodiment of my inventioncomprises an envelope I0, preferably in the form of a tube. The envelopeI0 is of glass or other suitable electrical insulating material and isformed at one end, its end A, with a reentrant portion II whichV isdoubled back on the adjacent envelope walls and extends Aaxiallyinwardly of the envelope, as shown. A cup-like cylindrical anode I2 ofmetal is sealed, vacuum tight, substantially at its open end to thereentrani; portion II and serves to complete the envelope. It will benoted that the arrangement is such that the closed end ofthe cup-likeanode I2 is disposed substantially at the end of the envelope.

`The envelope I0 on its other end, its end B,

is formed with an inwardly and axially extending tubular portion I3. Theportion I3 is closed ofi by a wall portion I4 which terminates in apinch I5 aboutvtwo lead wires I6 and I'I. The arrangement is such that avacuum tight seal is made between the wires I6 and I'I and the portionl5. I Y

A metal sleeve I8 is provided on the tubular envelope portion I3, and asleeve of metal mesh I9 is disposed between the sleeve I8 and theenvelope portion I3. The sleeve I8 is formed with a longitudinal slot 20and a transverse slot 2I, and two sleeve portions 22 which maybe sprunginwardly by suitable means are thus provided. A ring 23 fits about thesleeve I8 and lover the portions 22 and is provided with two screws 24threaded therein, each of the screws being disposed over one of theportions 22. The sleeve I8 is made to t tightly on the envelope portionI3 by tightening the screws 24 and there, by forcing the portions 22inwardly. The metal mesh I9 acts as a resilient means which helps toprevent breakage of the tubular portion I3 as the sleeve I8 is tightenedthereon.

A cylindrical plug-like supporting member is disposed in the sleeve I8and is held in such position by a screw 26. The supporting member 25 isprovided with four openings 21 which are equidistant from and are spacedregularly about the center of the supporting member 25. A sleeve 28 ofceramic or other insulating material is provided in each of the openings21; and metal posts 29, 39, 3| and 32 are disposed one in each of thesleeves 28. The supporting member 25 forms an anchor for the posts, andthe posts are firmly fixed relative to thesupporting member. It isapparent that each of the posts is electrically insulated from the otheryposts and from the supporting member.

The posts 29 and 30 are connected at their topsby a connecting portion33. A helical filament 34 is attached to the portion 33, and the portion33 serves as an upper terminal and support for .the filament. As shown,the posts 29 and and the connecting portion 33 are preferably formed ofa single piece of material.. A relatively short post 35 is fixed in thesupporting member 25 at its center and constitutes a lower terminal forthe filament 34. It will be noted that the filament A34. is disposedinthe anode and on the central axis of the anode, and that the posts 29,30, 3| and 32 are equidistant from and disposed regularly about thefilament ,34 and extend into the anode in directions substantiallyparallel to the central axis of the anode.

A wire supporting arm 36 is fastened to the post 3| and is attached tothe filament 34 at anl intermediate point thereof approximately onethirdthe distance from the terminal 35 to the terminal 33. A similarsupporting arm 3'1 is fastened to the post 32 and is ,attached to thefilament at an intermediate point thereof approximately two-thirds thedistance from the terminal 35 to the terminal 33.

The wire I6, leading into the tube, is connected to the supportingmember 25, and the other wire I1 is connected to the post 29 as shown. A

voltage applied between the leads I6 and I1 causes acurrent to flowthrough the lead I1, the post 29, the filament 34, and the terminal 35and finally through thesupporting member 25 to the lead I6.

It will be readily understood that the envelope I0 has the airsubstantially exhausted therefrom, and the cathode of the tube whichincludes the filament 34, the posts 29, 3|), 3| and 32 and thesupporting member 25, is in a sub-'- r stantial vacuum. With a suitablevoltage applied between the leads I6 and I1, suicient current flowsthrough the filament 34 so that electrons are emitted therefrom. Whenthe anode I2 is substantially more positive than the cathode, theelectrons emitted from the filament 34 travel to the anode. Theprincipal part of the electrons from the filament 34 travels to theinternal side face portion I2a of the anode, and a smaller part of theelectrons travels to the internal end face portion |2b of the anode.Inasmuch as the anode I2 surrounds the filament 34, substantially noneof the electrons therefrom reach the glass side walls of the tube, andsubstantially no electrical charge builds up on the tube walls. As aresult, the possibility of tube rupture due to excessive electricalcharge on the tube walls is minimized, and voltage drop across the tubedue toY such a charge is minimized. It will be noted Vthat the electronreceiving face portions I2a and |211 of the anode complete the envelopeof the rectifier tube; that is to say, the face portions I2a and |211form a part of the inner surface of the envelope.

The metal posts 29, 39, 3| and 32, disposed about the filament 34, serveas electrostatic shields for the filament. The filament 34 is positionedas closely as possible on the central axis of the anode I2, and theelectrostatic stresses in the filament due to the high voltages betweenthe anode and cathode of the tube are thus made small. However, when thefilament is operated at the high temperatures necessary for highquantity electron emission, as is desirable when rectifying a Voltagefor an X-ray tube, the filament is quite soft, and it is desirable toreduce the electrostatic stresses in the filament still further. Themetal posts 29, 30, 3| and 32 electrostatically shield the filament andreduce the electrostatic stresses therein, and the posts thus protectthe filament from breakage. The supporting arms 36 and 31 operate tohold the filament' substantially on the central axis of the anode I2regardless of the position in which the tube is operated. It is apparentthat the posts 29, 30, 3| and 32 have a two-fold function; the postselectrostatically shield the filament, and in addition the posts, withthe supporting arms 36 and 31 and the connecting portion 33, support thefilament at its top and at intermediate points. The post 29 furtherserves as an electricrsupply lead for the filament.

My improved rectier tube is quite short and compact, yet it has the highelectrical resistance between its anode and cathode necessary towithstand the high voltages used on vX-ray tubes. The electricalresistance between the anode and cathode of the valve tube varies withthe distance on the glass portion of the envelope betweenthe anode andcathode. This distance in my improved valve tube includes not only thedistance on the tubular portion I3 from the sleeve I8 to the end B ofthe tube plus the distance on the outer walls of the envelope I0 fromthe tube end B to the tube end A, but it alsol includes the distance onthe reentrant tube portion II from the tube end A to the anode I2. Bydoubling the outer walls of my improved tube back to form the reentrantportion .II, I have produced a tube having the requisite high electricalresistance between cathode and anode, and yet one that is substantiallyshorter in length than prior tubes having substantially the sameelectrical resistance. It will be noted that in my tube the reentrantportion II extends along and is separated from both the outer side wallsof the tube and the sides of the anode I2.

Myl improved rectier tube is preferably operated immersed in anelectrically insulating heat conducting liquid, preferably oil. Ahousing 38 for X-ray apparatusincluding my tube and a high voltagetransformer 39 is shown in Fig. 6. The housing 38 contains a body-ofelectrically insulating heat conducting liquid 40 which surrounds thetube and transformer. In the arrangement shownthe high voltage secondarycoils 4| are disposed over the primary winding 42, and the rectifiertube is supported by arms 43 mounted on the coils 4I.y The coils 4| areconnected in series,` and one of the coils is connected by a lead 44with the cathode 45 of an X-ray tube 46. Theother coil 4I is connectedby a lead 41 withthe anode I2; ofthe-'rectifier tube. The conductorIB-of therectifier tube is connected by a'lead'48 with the target 49 ofthe X-ray tube. Voltages are applied between the leads 50 and 5Iconnected to the cathode 45 of the X-ray tube for heating the cathode,between the leads 52 and 53 connected to the primary winding 42 of thetransformer, and between leads 54 and 55 connected to the primarywinding 56 of the filament transformer 51 which is immersed in theliquid and has its secondary winding 58 connected with the leads I6 andI1 for heating the cathode of the rectifier tube. In this arrangement,the rectifier tube rectifies the voltage of the secondary windings 4 Iand this rectified voltage is impressed across the X-ray tube 46.

In my improved rectifier tube arrangement, the reentrant portion II ofthe envelope being separated from the sides of the anode I2, the fluid40 on operation of the tube circulates about the sides of the anode aswell as about its closed end for cooling the anode. The anode I2 is ofsuitable metal of thin gauge and constitutes a part of the tube envelopein contact with the fluid 40, and heat developed at the electronreceiving surfaces I2a and I2b is effectively transferred to the fluid4l). The heat in the fluid 40 is transferred from the fluid to thehousing 38, and from the housing the heat is dissipated in thesurrounding air. The fluid 40 is electrically insulating and does notallow electric arcs to form between any of the leads or other apparatusin the housing 38.

My improved thermionic valve is compact and requires only a smallhousing space. Even though short, my improved valve nevertheless has ahigh electrical resistance between cathode and anode and is suitable foruse with the high voltages used on X-ray apparatus. The cathode of myimproved valve is of such construction that the filament iselectrostatically shielded, and the high voltage applied between theanode and cathode of the valve does not break the filament even thoughthe filament is heated to a high temperature as is preferable. Thefilament is supported by auxiliary supports, and my improved valve maybe operated in a horizontal or other position. The valve in my irnprovedarrangement is effectively cooled and even under high instantaneousoverload conditions the anode of the valve does not become heatedunduly. My improved thermionic valve arrangement is simple inconstruction and may be economically manufactured.

I do not intend to limit my invention to the details of constructionshown and described except only insofar as certain of the claims may beso limited as it will be apparent to those skilled in the art thatchanges in the construction and arrangement of the parts may be madewithout departing from the principles of the invention.

I claim:

l. In a valve of the type described, the combination of a hollow anode,an electron emitting filament in said anode, a plurality of spaced metalposts extending along and disposed about said filament, two of saidposts being connected at their tops by a connecting portion whichconstitutes a terminal and support for one end of said filament, atleast one of the other of said posts being provided with a supportingarm extending to an intermediate point of said lamentl for supportingthe filament, and a terminal for the other end of said filament.

2. In a valve of the type described, the combination of a hollow anode,an electron emitting filament in said anode, a pair of metal rodsextending along and disposed on opposite sides of said filament, and apair of supporting arms fastened to more than one of said rods, saidarms extending to and connected at spaced intermediate points of saidfilament for supporting the filament.

3. In a valve of the type described, the combination of a hollowcup-like anode, an electron emitting filament in said anode lying insubstantially the axis thereof, a plurality of metal posts extendingalong and parallel to said filament and all disposed equidistantly fromone another and from said filament and said anode axis, two of saidposts being connected together at similar ends by a connectionintersecting the anode axis, said connection constituting a terminal andsup- Dort for one end of said filament, a terminal for the other end ofsaid filament disposed in the anode axis, and supporting connectionsfrom different intermediate points of said filament to more than one ofthe other posts.

4. In a valve of the class described, the combination of a hollowcup-like anode, an electron emitting filament in said anode lyingsubstantially in the axis thereof, a pair of metal posts along andonopposite sides of said filament and interconnected at their tops, saidinterconnection `constituting a terminal and support for one end of saidfilament, a second pair of metal posts along and on opposite sides ofsaid filament with their tops separated, a support from an intermediatepoint of said filament-to one of said second pair of posts and anothersupport from another intermediate point of said filament to the other ofsaid second pair of posts, and a terminal for the other end of saidfilament.

5. In a valve of the class described, the combination of a hollowcup-like anode, an electron emitting filament in said anode lyingsubstantially in the axis thereof, a pair of metal posts along and onopposite sides of said filament and interconnected at their tops, saidinterconnection constituting a terminal and support for one end of saidfilament, a second pair of metal posts along and on opposite sides ofsaid filament with their tops separated, a support from an intermediatepoint of said filament to one of said second pair of posts and anothersupport from another intermediate point of said filament to the other ofsaid second pair of posts, and a terminal for the other end of saidfilament, said second pair of posts being diametrically opposite eachother to thereby maintain said filament substantially in the axis of theanode regardless of the angular position of the valve.

6. In a valve of the class described, the combination of a hollowcup-like anode, an electron emitting filament in said anode lyingsubstantially in the axis thereof, a plurality of spaced metal postsextending parallel to the anode axis and along and equidistantly andradially spaced from said filament, two of said posts diametricallyopposite to each other being interconnected at the ends thereof withinsaid anode, said interconnection constituting a terminal and support forone end of said filament, supports extending from different intermediatepoints of said filament to all of the others of said posts to applyholding forces in more than one direction to thereby maintain saidfilament substantially in the anode axis regardless of the angularposition of the valve, and a terminal for the other end of said filamentcoincident with the anode axis.

JOSEPH J. HEGER.

